They are Uzi mags, avec followers. But the AR series followers have that little bolt hold open piece on the back. That piece is also the thing that makes the original Colt mags hard to load past about 4-5 rounds. And I'm only relaying information learned by my prior to the laws that made us safe today.
Point is...... and there is one, maybe one of the larger surplus dealers have some old parts sitting around. Maybe even Numric/Gunparts Corp?????